The present invention relates to a method for preparing film coated pharmaceutical preparations composed of a solid drug and a coating layer on the outer surface thereof and a method for improving properties of film coated pharmaceutical preparations likewise comprised of a solid drug and a coating layer on the outer surface thereof, which makes it possible to impart an excellent appearance to the film coated pharmaceutical preparations.
Heretofore, solid drugs such as tablets have been subjected to film coating treatment to form film coated pharmaceutical preparations therefrom. Such a coated film serves to prevent uncomfortable tastes of drugs from giving out therefrom, as well as to protect effective components of the drugs from causing property change and to control the releasing behaviors of the effective components in the digestive system after an administration thereof. In view of enhancing the reliability of drugs and the acceptability of their appearance as medicines, it has been desired to impart a snow white and beautiful finish to such a coating layer. In some cases, coated films are pigmented by incorporating, into the basic materials (basic coating materials) for forming the coating layer, a coloring material during the film coating operations. In such a case, it is desired for the coated film to have a finish of a bright color tone.
However, the basic materials conventionally employed are slightly gray colored or yellow colored ones and thus it has been very difficult to obtain snow white basic coating materials. If a film coated pharmaceutical preparations are prepared utilizing such a basic coating material, the color of the resultant coating layer thereof is not completely white but they are slightly pigmented. On the other hand, if a coloring material is incorporated into the basic coating material, the color of the resultant coating layer of the film coated pharmaceutical preparations is not clear because of the influence of the color of the basic coating material. Therefore, the acceptability of the visual appearance of the drugs is greatly reduced and the commercial value thereof is also lowered due to such coloration.
Furthermore, a white pigment has been incorporated into the basic coating material to improve the whiteness thereof. However, the use of such white pigment leads to the reduction of the strength of the coating layer, which in turn leads to undesirable releasing behavior and possible property change of the effective components.